Ash Content in Your Forages
The ash content in forages is rarely discussed or considered in dairy ration balancing.
Overlooking ash content, however, when formulating dairy cow diets can cause serious problems.
Forage and total mixed rations (TMR) high in total ash content can skew energy estimates
leading to flawed dry matter intake estimates. Too much ash in forages can distort ration levels
leading to incorrect nutrient levels that can harm a dairy nutrition program’s performance.
What is ash?
Ash is simply the total mineral content of a forage or diet. Minerals in feed can be broken down
into two general categories: those which plants normally contain (calcium, potassium, phosphorus
and magnesium) and those primarily associated with soil. Ash from soil can become mixed with
forages during harvest, storage and feed out.
What are the normal levels of ash in forages?
Graphs 1 to 3 (adapted from Focus on Forage – Vol. 7: No. 1 by Pat Hoffman) show the normal
distribution of 1,000 samples of legume-grass, corn silage and TMR samples tested for ash
levels. The typical ash content for legumes is 8-10% on a dry matter basis. The normal ash
content for corn silage is approximately 5% on a dry matter basis.
To understand what this means, imagine the following example. Suppose you have a ration
requiring
Graph 1. Distribution of Ash Content in 1,000 Legume-Grass Samples
Number of Samples
300
250
200
150
100
50
0
4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0
Ash, % of DM
Graph 2. Distribution of Ash Content in 1,000 Corn Silage Samples
N um b er of Sa m ple s
5 00
4 00
3 00
2 00
1 00
0
2 .0
4 .0
6 .0
8 .0
A s h , % o f DM
1 0.0
N um ber of Sam ples
Graph 3. Distribution of Ash Content in 1,000 Total Mixed Rations
400
350
300
250
200
150
100
50
0
4.0
6.0
8.0 10.0 12.0 14.0 16.0
A s h, % of DM
15 pounds of haylage (dry matter.) If that haylage contains 10% ash, it contributes 1 ½ pounds
of ash to the total diet.
What is the problem with ash?
The problem with feeding ash is that it does not contribute any calories (energy) to the diet.
Ash is devoid of protein, calories, energy and nutrients that a dairy cow can ferment in her
rumen. If the ration being fed appears well balanced, but herd production is disappointing, you
may have an ash problem. Ash is a difficult component to grasp and is often not considered
until there is an unexplained problem with performance. Many, but not all, commercial testing
laboratories routinely include ash content in their typical forage analysis.
What is the cause of high ash levels?
New disc-type haybines, which lift forages with negative air pressure, may add soil to the
forage. Forages lodged due to wind and rain may be contaminated with soil. Also, forages
stored on earthen bases in bunkers, piles and bags may have soil contamination incorporated
during loading. Additionally, pack tractors can drag soil into these storage systems during filling
and packing. Many of these situations are unavoidable, but paying close attention to ash
content in forages and TMRs can help reduce high ash content problems.
What is the solution?
Knowing the level is half the battle: One of the single most important steps a producer can
take to head off problems is to test ash levels in forages. Ash content in a forage or TMR is
easy to measure in a forage testing laboratory. Testing requires little equipment and is usually
inexpensive to perform.
Take the time to decrease soil contamination: Operating clean equipment during harvest is
advised. Make sure discbines and rakes are set at the correct ground clearance to avoid
incorporating unnecessary amounts of soil. When constructing a drive-over pile on earthen
bases try to minimize dirt dragged into the pile and make sure the packing tractors have clean
tires. If ash levels in forage are too high for your ration, dilute the total ash content by feeding
less of that particular forage.
Awareness is key: Overall, being aware of ash content and taking steps to avoid
incorporating unnecessary amounts of ash in rations are part of a proactive forage
management program.